The present invention relates to a hinge. More particularly this invention concerns a hinge for interconnecting the seat part and the back part of a motor-vehicle seat.
The back part of the front seat of a motor vehicle can normally be pivoted about an axis transverse to the normal direction of travel of the vehicle so that the seat can be adjusted for the comfort of the passenger. For such adjustment it is necessary not only that a plurality of different positions be assumable by the back part relative to the seat part, but also that the back part be held very rigidly and solidly in place once its proper position has been selected. Forward pivoting of the back part of the seat during a collision or rapid stop must be prevented in order to avoid injury to a front-seat passenger.
A typical such mechanism is a hinge having a pair of hinge elements, one of which is secured to the back part of the seat and the other of which is secured to the seat part. One of these elements is formed with an annular array of inwardly directed teeth. The other element of the hinge carries one or more pawls having outwardly directed teeth and pivotal so that the teeth on the pawls can be brought into engagement with the teeth on the other element. Means, normally in the form of a cam operated by a radially extending handle, is provided for pivoting these pawls.
Thus with such an arrangement the seat position is adjusted by actuating the handle so as to pull the teeth of the pawls out of mesh with the teeth of the other hinge element. The seat is then moved to the proper position and the handle is returned to its original position to lock the hinge elements angularly relative to each other.
Each of these pawls is normally pivoted in that hinge element which does not have the annular array of teeth by means of a pin formed directly on the pawl and journalled in the respective hinge element. Such construction allows the hinge to be produced at approachable cost, yet offers a relatively long service life. The principal disadvantage of this system is that in case of an accident or the like wherein the seat back is stressed very forcefully forwardly it is possible for these pivot pins on the pawls to break off. Once broken off the pawls can then move freely and the seat back can correspondingly pivot forwardly. Thus a common occurrence in the known hinges is that they fail to hold the seat back relative to the seat part at that time when such securing is most important.